JP5189204B2 - Method for performing random access procedure and terminal thereof - Google Patents

Abstract

A method of performing a random access channel (RACH) procedure between a mobile terminal and a network includes the steps of detecting whether a random access response (RAR) is received from the network within a certain time period, the RAR including information about a random access channel (RACH) preamble transmitted to the network; and if the RAR is not received within the certain time period or if the information about the transmitted RACH preamble included in the RAR does not match the transmitted RACH preamble, performing a first procedure to detect failures in the RACH procedure; and if the RAR is received within the certain time period and if the information about the transmitted RACH preamble included in the RAR matches the transmitted RACH preamble, performing a second procedure to detect failures in the RACH procedure.

Description

  The present invention relates to an apparatus and method for performing a random access procedure.

  In the prior art, the random access procedure cannot be performed efficiently. As described above, since the related art cannot sufficiently cope with the above problem, an appropriate solution is not presented.

  The inventors have recognized at least the shortcomings of the prior art identified above. Various features to be described later have been devised based on such recognition, and a random access procedure between the mobile terminal and the network is performed based on the characteristics of a random access channel (RACH) preamble. As a result, the downlink channel can be monitored more efficiently, and the power consumption can be reduced.

It is a figure which shows an example of the structure of E-UMTS (Evolved Universal Mobile Telecommunications System). It is a figure which shows an example of the structure of the radio | wireless interface protocol (Radio Interface Protocol) in the control plane between a mobile terminal (UE) and a network (eNB, MME). It is a figure which shows an example of the structure of the radio | wireless interface protocol in the user plane between a mobile terminal (UE) and a network (eNB, SAE gateway). It is a flowchart which shows an example of the random access procedure of the contention based (contention based random access procedure) between a mobile terminal (UE) and a base station (eNB). It is a figure which shows an example of the relationship between the partial channels (PDCCH (Physical Downlink Control CHannel) and PDSCH) between a base station and a mobile terminal. FIG. 6 is a conceptual diagram illustrating a contention-based random access procedure performed by a mobile terminal according to an embodiment of the present invention. FIG. 2 is a conceptual diagram illustrating a non-contention based random access procedure performed by a mobile terminal according to an embodiment of the present invention. FIG. 6 is a conceptual diagram illustrating a contention-based random access procedure performed by a mobile terminal when a RACH procedure fails according to an embodiment of the present invention. 6 is a flowchart illustrating a random access procedure performed by a mobile terminal according to an embodiment of the present invention. It is a conceptual diagram explaining the random access procedure of FIG.

  The concept and features of the present invention will be described in terms of an LTE (Long Term Evolution) system or a so-called 4G communication system that has advanced from the current 3GPP (Third Generation Partnership Project) technology. However, the details do not limit the various features described herein, and can be applied to other types of mobile and / or wireless communication systems and methods.

  Hereinafter, the term “mobile terminal” refers to a variety of mobile communication terminals, user equipment (UE), mobile equipment (ME), and other devices that support various types of wireless communication technologies. Used to indicate a type of user equipment.

  Embodiments of the present invention relate to a method for transmitting and receiving data between a base station (eg, Node B, eNB, access point, etc.) and a mobile station (eg, mobile terminal, UE, user equipment, etc.) in an LTE system. Since the reception time of the downlink channel is determined according to the characteristics of the preamble of the mobile terminal performing random access, the power consumption of the mobile terminal can be reduced to the minimum, and the downlink channel can be monitored more efficiently Can do.

  Second generation (2G) mobile communication relates to a method of transmitting and receiving audio signals in a digital manner, and includes technologies such as CDMA and GSM. GPRS was developed with an improved technology from the GSM, which is a technology for providing a packet switched data service based on the GSM system.

  The third generation (3G) mobile communication relates to a method for enabling transmission / reception of not only audio but also video and data. 3GPP developed IMT-2000 technology and adopted WCDMA as a radio access technology (RAT). A combination of IMT-2000 and WCDMA is called UMTS (Universal Mobile Telecommunication System), which includes UMTS Terrestrial Radio Access Network (UTRAN).

  In 3rd generation mobile communications, data traffic is expected to increase rapidly, and standardization work is underway to build an LTE network that supports a wider bandwidth. LTE technology has been adopted for E-UMTS (Evolved-UMTS), which includes E-UTRAN (Evolved-UTRAN) using OFDMA (Orthogonal Frequency Division Multiple Access) as a radio access technology (RAT).

  FIG. 1 is a diagram illustrating an example of a structure of E-UMTS that is one form of a mobile communication system. The E-UMTS system has evolved from the UMTS system and is a basic standardization work currently underway by the 3GPP organization. The E-UMTS system can also be referred to as an LTE system, which is a form of so-called 4G or next generation system that has evolved from the current third generation mobile communication system.

  The E-UMTS network 100 is generally divided into an E-UTRAN 110 and a CN (Core Network). E-UTRAN is a mobile terminal (eg, User Equipment (UE), mobile station, handset, mobile phone, etc.) 112, a base station (eg, eNode B, access point (AP), network node, etc.) 114, 116, 118. , Serving gateways (S-GW) 122 and 124 connected to an external network located at the end of the network, and mobility management entities (MME) 122 and 124 that manage mobility of the mobile terminal including. One eNode B has at least one cell (or region, region, etc.).

  2 and 3 show a radio interface protocol between a mobile terminal and a base station conforming to the 3GPP radio access network standard. The radio interface protocol is horizontally divided into a physical layer, a data link layer, and a network layer, and vertically divided into a user plane for data information transmission and a control plane for control signal transmission. The Such a protocol layer includes L1 (first layer), L2 (second layer), and L3 (lower layer) of the Open System Interconnection (OSI) standard model known in communication systems. 3rd layer).

  The radio protocol control plane of FIG. 2 and the radio protocol user plane of FIG. 3 will be described below.

  In the first layer, the physical layers 225-245 and 325-345 provide an information transfer service using at least one physical channel. The physical layer is connected to upper medium access control (MAC) layers 224-244 and 324-344 via at least one transport channel, and is connected to the MAC layer via the transport channel. Data between physical layers is transmitted. Further, data is transmitted through at least one physical channel between each physical layer, that is, between the physical layer on the transmission side and the physical layer on the reception side.

  The physical channels existing in the physical layer on the transmission side and the reception side include SCH (Synchronization Channel), PCCPCH (Primary Common Control Physical Channel), SCCPCH (Secondary Common Control Physical Channel), DPCH (Dedicated Physical Channel), PICH (Paging Indicator Channel), PRACH (Physical Random Access Channel), PDCCH, PDSCH (Physical Downlink Shared Channel), and the like.

  In L2 (second layer), the MAC layer provides services to upper radio link control layers 223-243 and 323-343 via at least one logical channel. Based on the type of information to be transmitted, the logical channel is divided into a control channel used for transmitting control plane data and a traffic channel used for transmitting user plane data.

  In L2 (layer 2), the RLC layer supports reliable data transmission. Each radio bearer (RB) is in charge of QoS (Quality of Service) guarantee and data transmission associated therewith. To guarantee RB-specific QoS, one or two independent RLC entities are provided for each RB, and three types of RLC modes (Transparent Mode (Transparent Mode) are supported to support various QoS requirements. TM), Unacknowledged Mode (UM), and Acknowledged Mode (AM)).

  In L2 (second layer), a PDCP (Packet Data Convergence Protocol) layer 322-342 is relatively small in size so as to efficiently transmit IP packets in a wireless section with a small bandwidth (such as IPv4 and IPv6). A header compression function is executed to reduce the header size for IP packets that contain large and unnecessary control information. The PDCP layer is used to encrypt control plane data such as an RRC (Radio Resource Control) message. The PDCP layer can also encrypt user plane data.

  The RRC layers 222-242 located at the highest level of the third layer are defined only in the control plane, and are responsible for controlling logical channels, transport channels, and physical channels with respect to radio bearer (RB) setup, reconfiguration, and release. . Here, the radio bearer means a service provided by the second layer for data transmission between the UE and the E-UTRAN.

  Hereinafter, features of the RACH procedure will be described. The RACH procedure is used to transmit relatively short data on the uplink. In particular, the RACH procedure is used when there is a signaling message or user data to be transmitted on the uplink by a mobile terminal not assigned a dedicated radio resource. Alternatively, it may be used when the base station has to instruct the mobile terminal to perform the RACH procedure.

  Next, a random access procedure provided by the LTE system will be described. The random access procedure provided by the LTE system is divided into a contention based random access procedure and a non-contention based random access procedure. The partition is used by the mobile terminal directly selecting the random access preamble used in the random access procedure (ie, the mobile terminal's MAC selects the preamble) or by the base station (ie, by explicit signaling). Received information on the preamble).

  In a non-contention based random access procedure, the mobile terminal uses a preamble that the base station directly assigns to the mobile terminal. Therefore, when the base station allocates a specific random access preamble to the mobile terminal, the random access preamble is used only by the mobile terminal, and other mobile terminals do not use the random access preamble. Accordingly, since a one-to-one relationship is established between the random access preamble and the terminals using the random access preamble, there is no contention (or collision) between a plurality of mobile terminals. In this case, when the random access preamble is received, the base station can immediately recognize which mobile terminal has transmitted the random access preamble, and thus can be said to operate more efficiently.

  On the other hand, in the contention-based random access procedure, a specific random access preamble is selected from the random access preambles that can be used by the mobile terminal and transmitted, so the possibility that multiple mobile terminals use the same random access preamble. There is. Therefore, even if a specific random access preamble is received, the base station cannot accurately recognize which mobile terminal transmitted the random access preamble.

The mobile terminal performs a random access procedure at least in the following example.
-When there is no radio resource control connection (RRC Connection) with the base station, and when initial connection (initial access)-When the mobile terminal first connects to the target cell during the handover process・ Uplink data is generated when the uplink time is not synchronized or the specified radio resource used for appropriate request of radio resource is not yet allocated. ・ Radio link failure ) Or correction procedure in case of handover failure (eg decoding, reconfiguration, recovery, etc.) Based on the above description, between the mobile terminal and the base station for the contention based random access procedure Will be described with reference to FIG. 4 (including steps 1 to 4).

Step 1)
In the contention-based random access procedure, the mobile terminal selects one random access preamble (for example, randomly) from the set of random access preambles indicated by the system information or the handover instruction, and then transmits the random access preamble PRACH resources that can be used for transmission are selected and transmitted. Here, the preamble is referred to as RACH MSG 1. Selection of a preamble directly (randomly) by a mobile terminal (that is, a preamble directly selected by the MAC) is called a contention-based RACH procedure, and the preamble is a contention-based preamble (contention -based preamble). When the mobile terminal is assigned the preamble directly from the network via RRC or PDCCH (that is, an explicitly signaled preamble), it is referred to as a non-contention based RACH procedure, and the preamble is referred to as a dedicated preamble. ).

Step 2)
When transmitting the random access preamble thus selected, the mobile terminal attempts to receive the random access response within the random access response reception window indicated by the system information or the handover instruction from the base station. More specifically, random access response information (generally referred to as RACH MSG 2) is transmitted in the form of a MAC PDU, and the MAC PDU is transmitted on the PDSCH. Also, information on the radio resource for the PDSCH is transmitted on the PDCCH using RA-RNTI.

  The random access response includes a random access preamble identifier (ID), a UL grant (for uplink radio resources), a temporary C-RNTI (temporary cell identifier), and a time alignment command (for time synchronization adjustment). Value).

  If the random access preamble identifier (ID) is the same (ie, matches) as the random access preamble transmitted in step 1), the mobile terminal may be in uplink radio, especially if a contention based random access preamble procedure is in progress. Step 3) is performed using information about the resource. If a dedicated preamble is used in step 1), and if the random access preamble identifier (ID) included in RACH MSG 2 and the random access preamble transmitted by the mobile terminal are the same (ie match), the RACH procedure is It is considered to stop or end.

Step 3)
When the mobile terminal receives a meaningful random access response (RAR; RACH response) (that is, when RAR is a valid response for the mobile terminal), it processes the information in the random access response, respectively. That is, the mobile terminal applies the time alignment command and saves the temporary C-RNTI. In addition, the UL grant is used to transmit data stored in the terminal buffer or newly generated data to the base station. Here, data (ie, MAC PDU) transmitted using the UL grant is generally referred to as RACH MSG 3. The mobile terminal identifier (ID) must be included in the data included in the UL grant (ie, RACH MSG 3). In the contention-based random access process, since the base station cannot determine which terminal is performing the random access procedure, the mobile terminal is identified in order to resolve future contention or collision. Because we need information that can be used.

  In the above procedure, there are two methods for including the identifier of the mobile terminal. In the first method, when the mobile terminal already has a valid cell identifier (C-RNTI) assigned from the base station of the corresponding cell before the random access procedure, the mobile terminal uses the UL grant to assign the cell identifier. Send. In the second method, when a unique cell identifier is not assigned before the random access procedure, the mobile terminal performs transmission including a core network identifier (for example, S-TMSI, Random ID, etc.) of the mobile terminal. . After transmitting data by the UL grant, the mobile terminal starts a contention resolution timer for contention (collision) problem resolution.

Step 4)
Data is transmitted using the UL grant included in the random access response (including the identifier of the mobile terminal), and then the mobile terminal waits for an instruction from the base station for contention resolution. That is, it tries to receive the PDCCH in order to receive a specific message. There are two methods for receiving the PDCCH. As described above, when the identifier transmitted using the UL grant is a cell identifier (C-RNTI) allocated from the eNB to the mobile terminal, the mobile terminal uses the cell identifier of the mobile terminal. If the identifier is an identifier assigned through the core network, the PDCCH is received using the temporary C-RNTI included in the random access response.

  Thereafter, in the former case (ie, C-RNTI), if the PDCCH (hereinafter, RACH MSG 4) is received before the contention resolution timer expires (using the cell identifier of the mobile terminal), the mobile terminal Determines that the random access procedure has been normally performed, and ends the random access procedure. In the latter case (ie, temporary C-RNTI), if the PDCCH is received by the temporary cell identifier before the contention resolution timer expires, the data transmitted by the PDSCH indicated by the PDCCH (hereinafter, RACH MSG 4 ) If the data includes the mobile terminal's own unique identifier, it is determined that the mobile terminal has normally performed the random access procedure, and the random access procedure is terminated. The message or MAC PDU received in step 4) is generally referred to as RACH MSG 4.

Step 5)
If the contention resolution timer expires (ie, a temporary C-RNTI or cell identifier for the mobile terminal has not been received before the contention resolution timer expires), the mobile terminal has failed the RACH procedure Judge that As a result, an appropriate back-off timer is activated (started), and after the expiration of the back-off timer, the RACH procedure starting from step 1) is resumed.

  Hereinafter, a method in which the mobile terminal receives downlink data in the LTE system will be described.

  In the downlink, there are basically two physical channels, PDCCH and PDSCH. The PDCCH is not directly related to transmission of user data, and is used for transmission of control information necessary to execute (use) a physical channel. In short, it can be said that the PDCCH is used to control other physical channels. In particular, the PDCCH is used for transmitting information necessary for the mobile terminal to receive the PDSCH. Regarding data transmitted using a specific frequency band at a specific time, information such as which terminal is used and what size of data is transmitted is transmitted on the PDCCH. Accordingly, each mobile terminal receives a PDCCH at a specific time (for example, TTI (Transmit Time Interval)) and confirms whether (to be received) data is transmitted. If the data (to be received) indicates that the data has actually been transmitted, the PDSCH is further received using information (such as an appropriate frequency) indicated by the PDCCH. That is, information on which mobile terminal (that is, one or a plurality of terminals) the PDSCH data is transmitted, information on how the mobile terminal should receive and decode the PDSCH data, etc. Can be said to be transmitted using a physical channel, that is, PDCCH.

  For example, in a specific subframe, radio resource information A (for example, frequency allocation), transmission format information B (for example, transmission block size, modulation scheme, encoding information, etc.), RNTI (Radio Network Temporary Identity) information C is CRC (Cyclic Redundancy Check) It is assumed that the data is masked and transmitted on the PDCCH. At least one terminal in the corresponding cell monitors the PDCCH using RNTI information of the terminal. According to the above process, in the mobile terminal having the RNTI information C, no CRC error occurs when the PDCCH is decoded. Therefore, the mobile terminal receives the data by decoding the PDSCH using the transmission format information B and the radio resource information A. On the other hand, in a mobile terminal that does not have the RNTI information C, a CRC error occurs when the PDCCH is decoded. Therefore, the mobile terminal does not receive PDSCH.

  According to the above process, an RNTI (Radio Network Temporary Identifier) is transmitted on each PDCCH to notify which mobile terminal a radio resource is allocated. The RNTI is divided into a dedicated RNTI and a shared RNTI. The dedicated RNTI is assigned to one mobile terminal and used for transmission / reception of data corresponding to the mobile terminal. The dedicated RNTI is assigned only to mobile terminals whose information is registered in the base station (eNB). On the other hand, the shared RNTI is used for transmitting / receiving data to / from a base station by a mobile terminal to which no information is registered in the base station (eNB) and is not assigned a dedicated RNTI (like system information). B) Used to transmit information commonly applied to a plurality of mobile terminals.

  On the other hand, two main elements constituting the E-UTRAN are a base station and a mobile terminal. Radio resources in one cell are composed of uplink radio resources and downlink radio resources. The base station is responsible for allocation and control of the uplink and downlink radio resources of the cell. That is, the base station determines which mobile terminal uses which radio resource at a certain moment. For example, the base station may decide to assign a frequency of 100 Mhz to 101 Mhz to User 1 for 0.2 second downlink data transmission after 3.2 seconds. In addition, after making such a determination, the base station notifies the relevant mobile terminal of this fact and causes the mobile terminal to receive downlink data. Similarly, the base station determines when and how much radio resource is used to transmit data on an uplink to a mobile terminal, and the base station notifies the mobile terminal of this determination and notifies the mobile terminal. Data is transmitted using a predetermined radio resource at a predetermined time.

  Unlike the prior art, if the base station manages radio resources in a dynamic manner in this way, efficient use of radio resources becomes possible. Usually, one terminal continuously uses one radio resource while a call is connected. This is undesirable in view of the fact that many services are now based on IP packets. This is because most packet services do not generate packets continuously during the call connection time, but have many time intervals during which nothing is transmitted during the call. Nevertheless, it is inefficient to continuously allocate radio resources to one mobile terminal. In order to solve this, the mobile terminal of the E-UTRAN system uses a method of allocating radio resources to the mobile terminal only when there is service data.

  Hereinafter, a part of the concept of DRX will be described. DRX refers to discontinuous reception, and when the base station and the mobile terminal communicate with each other, the base station should transmit information on radio resource allocation to the mobile terminal when (ie, at which time). It means actions related to kika. That is, the mobile terminal constantly monitors the downlink channel, particularly the PDCCH, which leads to undesirable power consumption in the mobile terminal. Therefore, in order to solve this problem, the base station sends the radio resource allocation information to the mobile terminal using the PDCCH only at a specific time according to a predetermined rule specified in advance by the mobile terminal and the base station. As a result, the mobile terminal only needs to monitor the PDCCH at the specific time, so that power consumption can be reduced.

  Some types of DRX operations are performed in the following manner.

  First, the active time is defined. This active time means the time that the mobile terminal has to start up (from the idle state) and monitor the downlink channel, ie PDCCH. After this active time, the mobile terminal does not need to monitor the PDCCH.

  The active time has the following time intervals.

1) Time during which the on-duration timer, DRX inactivity timer, DRX retransmission timer, or contention resolution timer is active (= condition 1)
2) Time when scheduling request process is performed 3) Time when radio resource allocation message (for retransmission) is transmitted for uplink transmission 4) After receiving RACH MSG 2 (first transmission or new transmission) Time to receive C-RNTI or temporary C-RNTI (notifying the allocation of radio resources for the
Hereinafter, a technical solution provided by an embodiment of the present invention will be described with reference to the technical description.

  In order to reduce power consumption, DRX for RACH procedure is also performed. The aforementioned active time can also be considered from the viewpoint of the RACH procedure.

  6 and 7 show the RACH procedure performed by the mobile terminal for (a) contention based and (b) non-contention based situations. (A) In the contention-based RACH procedure, the active time means a period during which the mobile terminal has to monitor the downlink channel. Unlike the contention based RACH procedure, (b) in the non-contention based RACH procedure, there is no RACH MSG 3 transmission in progress. Also, temporary C-RNTI is not used.

  Referring to FIG. 6, when the mobile terminal monitors the downlink channel (ie, PDCCH), discontinuous reception (DRX) is performed in connection with the RACH procedure to reduce power consumption.

  Since this is a contention-based random access procedure, the mobile terminal selects a preamble and transmits the selected preamble to the base station (network) (S1 and S2). When the mobile terminal receives a random access response (that is, RACH MSG 2) from the base station, the mobile terminal individually processes information included in the random access response (S3). In addition, as a procedure for the mobile terminal to receive C-RNTI or temporary C-RNTI for notifying radio resource allocation from the base station, data transmitted by an uplink (UL) grant (that is, RACH MSG 3). (MAC PDU) to be sent (S4). In addition, the downlink channel (C-RNTI or temporary C-RNTI is transmitted) is monitored until the C-RNTI or temporary C-RNTI is actually transmitted after the preamble is selected (S5). . Here, the DRX timer is activated (or started) and becomes active until the C-RNTI or the temporary C-RNTI is received after the RACH MSG 2 is received. The contention-based resolution timer runs (starts) after sending RACH MSG 3 until it receives a C-RNTI or a temporary C-RNTI.

  FIG. 7 is a conceptual diagram illustrating a non-contention based random access procedure performed by a mobile terminal according to an embodiment of the present invention. Compared with FIG. 6, in the non-contention based random access situation, the mobile terminal does not perform the process of transmitting RACH MSG 3 to the base station (ie, S4 in FIG. 6). Also, temporary C-RNTI is not used in non-contention based random access situations. Here, the monitoring period or section of the downlink channel according to the RACH procedure is the same as in FIG.

  In FIG. 6, the contention-based RACH procedure indicates a situation where the mobile terminal succeeds in the RACH procedure. However, FIG. 8 shows a failure situation when the RACH procedure of the mobile terminal actually fails, that is, when the terminal has not received C-RNTI or temporary C-RNTI from the base station.

  In FIG. 8, the active time 1 is a time interval defined by the above-described active condition 4, and the active time 2 is a time interval defined by the above-described active time condition 1.

  As shown in FIG. 8, according to the definition of the active time described above, the downlink channel is monitored also in the back-off time. However, since the actual backoff time is not the time interval during which the contention resolution timer operates, the network does not allocate radio resources to the mobile terminal using C-RNTI or temporary C-RNTI. Therefore, since the mobile terminal does not need to actually monitor, power is unnecessarily consumed at such a time interval.

  In order to solve such a problem, when a downlink channel is monitored by performing a RACH procedure to receive scheduling information, the mobile terminal has to receive the downlink channel in a more efficient manner.

  To achieve this, determine whether the downlink channel should be monitored at a specific time (or during a specific time interval) based on information about the type of procedure the mobile terminal is currently performing Propose so.

  The mobile terminal can determine whether the downlink channel should be monitored according to whether the procedure being performed is a random access (RACH) procedure.

  When performing downlink channel monitoring, in order to determine whether or not downlink channel monitoring actually needs to be actually performed at a specific time (or period), the mobile terminal performs the RACH procedure described above. In the case of a procedure, information on the particular type of RACH procedure being performed must be consulted.

  That is, the mobile terminal determines whether to monitor the downlink channel in consideration of whether the contention-based RACH procedure is used or the non-contention-based RACH procedure is used.

  Contention-based RACH procedure means that the mobile terminal selects (randomly or by some other criteria) the RACH preamble used for the RACH procedure. That is, in this case, the MAC entity (of the mobile terminal) is considered to start the RACH procedure. Therefore, the MAC entity selects a preamble to be used.

  Non-contention based RACH procedure means that the RACH procedure is performed by the mobile terminal using a specific RACH preamble indicated directly (explicitly).

  Details of the procedure will be described below.

  In determining whether to receive the downlink channel according to the type of RACH procedure used, the following matters are referred to. After the mobile terminal starts the RACH procedure, it checks whether the RACH procedure is a contention based RACH procedure or a non-contention based RACH procedure.

  For non-contention based RACH procedures, during the period between receiving RACH MSG 2 (random access response) and receiving C-RNTI (indicating radio resource allocation for new transmission) on PDCCH Monitor the downlink channel. That is, the time interval from the reception of RACH MSG 2 (random access response) to the reception of C-RNTI (indicating radio resource allocation for new transmission) on PDCCH is included in the active time.

  For contention-based RACH procedures, the period of time between receiving RACH MSG 2 (ie, random access response) and receiving C-RNTI (indicating radio resource allocation for new transmission) on PDCCH Meanwhile, it is not necessary to monitor the downlink channel. That is, a time interval from receiving RACH MSG 2 (random access response) to receiving C-RNTI (indicating radio resource allocation for new transmission) on PDCCH is not included in the active time.

  That is, the time interval (or period) that begins when a RACH MSG 2 (ie, random access response) is received and ends when a C-RNTI (indicating radio resource allocation for new transmission) is received on the PDCCH Is not included in the active time for contention based RACH procedures, but is included in the active time for non-contention based RACH procedures.

  In other words, the definition of active time according to condition 4 (described above) applies to RACH procedures that are non-contention based RACH procedures (ie, when the RACH preamble is assigned directly from an external source to the MAC entity), Condition 4 does not apply to other situations.

  Therefore, in the embodiment of the present invention, the RACH procedure used is confirmed to determine whether it is contention-based or non-contention-based, and RACH MSG 2 is received according to the result. The time interval until receiving C-RNTI type information indicating the allocation of radio resources for new transmission on the PDCCH is included in the active time for determining the downlink channel.

  FIG. 9 is a flowchart illustrating a random access procedure performed by the mobile terminal according to an embodiment, and FIG. 10 is a conceptual diagram illustrating the random access procedure of FIG.

  The MAC entity of the mobile terminal (UE) selects the RACH preamble and transmits the selected RACH preamble to the network (S10, S11). When the UE receives a random access response (RACH MSG 2) from the network, the information included in the RAR is processed (S12). That is, using the information included in the RAR, it is determined whether the RACH preamble is selected by the UE MAC or explicitly signaled (or selected) by the network (S13). If the RACH preamble is not selected by the UE's MAC, that is, if it is explicitly signaled by the network, the UE receives radio resource allocation information (or C-RNTI, etc.) received from the network. The downlink channel (PDCCH) is monitored until new transmission is indicated by the scheduling information (S14).

  However, if the RACH preamble is selected by the UE MAC, a contention resolution timer is started (S15). Thus, the operation of FIG. 9 can also be understood based on FIG. That is, as in the DRX procedure, when the UE receives a random access response (RACH MSG 2) from the network, the contention resolution timer is activated to monitor the downlink channel (PDCCH). However, if the C-RNTI cannot be received on the monitored downlink channel before the contention resolution timer expires, the UE performs the random access procedure again after the back-off time is applied. Here, the terminal does not monitor the downlink channel from the time when the operation of the contention resolution timer expires. The downlink channel is monitored when the random access process is performed again after the back-off time. As shown in FIGS. 9 and 10, since the UE does not monitor the downlink channel during the back-off time, power consumption due to unnecessary DRX operation can be avoided.

  The mobile terminal includes a communication module (hardware, software, or combination thereof) configured to implement the operations described with respect to FIGS. In addition, the mobile terminal according to the present invention includes various types of hardware such as input / output means (for example, a display screen, a keyboard, a speaker, etc.) and a microprocessor (or other control means) for controlling various operations, Includes software that implements the operation.

  FIG. 10 illustrates how the concept of an embodiment having the inventive features described herein can be implemented. Here, a situation in which the mobile terminal fails in the RACH procedure, that is, a case where C-RNTI or temporary C-RNTI is not received is shown.

  As shown in FIG. 10, since the contention-based RACH procedure is used, the active time defined by condition 4 (described above) is not applied. Therefore, the mobile terminal does not need to monitor the downlink channel during the time when the back-off time is applied. As a result, unnecessary power consumption can be reduced.

  By implementing the embodiments described herein, with respect to the downlink channel monitoring performed by the mobile terminal, a specific monitoring period (downlink channel, eg PDCCH) is set in an improved manner Thus, battery power consumption (that is, power source control) can be improved.

  Some details regarding the concepts and features of the embodiments described herein can also be summarized as follows.

  DRX Command MAC CE can be used to place the UE directly in a short or long DRX cycle. However, if a DRX Command MAC CE is received while the DRX short cycle timer is running, this timer must not be affected. When the timer is started again (i.e., restarted), the duration of the UE in the activated state increases, resulting in an increase in battery consumption. Such a situation occurs when a HARQ retransmission grant for a MAC PDU including a DRX Command MAC CE is received while the short DRX cycle timer is operating. Here, “start” and “restart” are distinguished, and “start” is used when the timer is not operating, while “restart” is used when the timer is operating. Thus, if the short DRX cycle timer is running, it will not start but may resume.

  However, the potential problems described above can be avoided by implementing the following concept. If a DRX Command MAC CE is received while the short DRX cycle timer is running, the MAC CE is ignored.

  The active time may include a “period of not receiving a PDCCH indicating a new transmission to the C-RNTI or temporary C-RNTI of the UE after successfully receiving a random access response (RAR)”. This includes the period between the RAR reception time and the start time of the contention resolution timer. Also, the UE monitors the DL channel longer than necessary. For example, even after the contention resolution timer expires because there is no temporary C-RNTI reception, the UE still monitors the DL channel.

  However, the potential problems described above can be avoided by implementing as follows. (For contention-based preamble) Set the active time between the time when the RAR is received normally and the time when the contention resolution timer is started.

  That is, the contention-based preamble situation can be clarified as described above. Regardless of other issues, the features described herein can be applied to a dedicated preamble situation if it must remain active until a C-RNTI is received.

  Hereinafter, maintenance of uplink time alignment will be described.

  The UE has a configurable time alignment timer. The time alignment timer is only valid for cells that have been configured and started.

When the time alignment timer is configured, the UE performs the following operation.
-When a timing advance MAC control element is received,
Apply the timing advance command,
• Start the time alignment timer (if it does not work) or restart the time alignment timer (if it is already running).
・ When a time alignment command is received in a random access response message,
When explicitly signaling the random access preamble and PRACH resource,
Apply the time alignment command
• Start the time alignment timer (if it does not work) or restart the time alignment timer (if it is already running).
・ Or, if the time alignment timer does not work or expires,
Apply the time alignment command
・ Start time alignment timer
・ If contention resolution is not successful, end the time alignment timer.
Or
・ Ignore the received time alignment command.
・ If the time alignment timer expires or does not work,
Use a random access procedure to obtain uplink time alignment before sending any uplink.
・ When the time alignment timer expires,
・ Release all PUCCH resources,
Release any allocated SRS resources.

  Hereinafter, discontinuous reception (DRX) will be described. Since the UE is configured by RRC with the DRX function, the UE does not continuously monitor the PDCCH. The DRX function includes a long DRX cycle, a DRX inactivity timer, a DRX retransmission timer, and a selectable short DRX cycle and a DRX short cycle timer.

When a DRX cycle is configured, the active time includes the following period.
The period during which the on-duration timer, DRX inactivity timer, DRX retransmission timer, or contention resolution timer is active. Or
A period during which the scheduling request is not completed. Or
A period during which an uplink grant for retransmission can occur. Or
-From the normal reception of a random access response (RAR) to the start of the contention resolution timer.
Here, the active time is also defined as follows.
If the random access preamble is not explicitly signaled, the period during which the PDCCH indicating a new transmission to the UE's C-RNTI has not been received after successfully receiving the random access response. Or
-The period during which the DL restart timer is operating. The DL restart timer starts when the RAR is received normally when the random access preamble is explicitly signaled (where the DL restart timer ends when the UE C-RNTI is received) (instead, dedicated The DL resolution timer can also be started when the preamble is received on the PDCCH). Or
• When a random access preamble is selected by the UE MAC, after successfully receiving a random access response (RAR), until starting a contention resolution timer.

When the DRX cycle is configured, the UE performs the following procedure in each subframe.
If [(SFN × 10) + subframe number] modulo (current DRX cycle) = DRX Start Offset, the on-duration timer is started.
If the HARQ RTT timer expires in this subframe and the data of the soft buffer in the corresponding HARQ process cannot be decoded normally,
-Start the DRX retransmission timer for the corresponding HARQ process.
When DRX Command MAC control element is received,
・ End the on-duration timer,
-Terminate the DRX inactivity timer.
If the DRX inactivity timer expires or a DRX Command MAC control element is received in this subframe,
・ If a short DRX cycle is configured,
・ If DRX short cycle timer does not work, start DRX short cycle timer,
Use a short DRX cycle.
Or
Use a long DRX cycle.
If the DRX short cycle timer expires in this subframe,
Use a long DRX cycle.
-During the active time, in the PDCCH subframe except when the subframe is required for uplink transmission for half-duplex FDD UE operation,
・ Monitor PDCCH,
If the PDCCH indicates DL transmission,
Start the HARQ RTT timer for the corresponding HARQ process,
-Terminate the DRX retransmission timer for the corresponding HARQ process.
If the PDCCH indicates a new transmission (DL or UL)
• Start or restart the DRX inactivity timer.
If DL allocation is configured in this subframe and PDCCH indicating DL transmission cannot be successfully decoded,
Start the HARQ RTT timer for the corresponding HARQ process,
• Do not report CQI and SRS if not in active time.

  Regardless of whether or not the UE is monitoring the PDCCH, the UE sends and receives HARQ feedback when expected.

  Hereinafter, embodiments described in this specification will be described in detail.

  In the prior art, when performing the RACH procedure, the contention-based RACH preamble and the non-contention-based RACH preamble are not distinguished. Such drawbacks can be overcome by defining active times and associated conditions. PDCCH needs to be continuously monitored between MSG 2 and MSG 4. After receiving MSG 2, it determines whether the RACH preamble is contention-based or non-contention-based, and applies the condition for contention-based or non-contention-based situations.

  Here, it should be noted that contention-based and non-contention-based RACH preamble characteristics may be described in other terms and expressions. For example, it was expressed that the PDCCH indicating the new transmission to the C-RNTI of the UE was not received after successfully receiving the random access response for the explicitly signaled preamble. Here, the term “explicitly signaled” usually refers to dedicated signaling, but there may be situations where the term “explicitly signaled” refers to non-dedicated signaling. A preamble that is not explicitly signaled is equivalent to a preamble that is not selected by the MAC. Further, if the PDCCH state is a specific value (= 00000), the procedure can return to the contention base.

  The present invention includes a step of transmitting a RACH preamble to the network, a step of determining whether the transmitted preamble has been explicitly signaled by the network, and a C received from the network if explicitly signaled. A method for performing discontinuous reception (DRX) comprising monitoring the downlink channel (PDCCH) until the RNTI indicates a new transmission and starting a contention resolution timer if not explicitly signaled. provide.

  Further, the present invention determines that a RACH preamble is transmitted to the network, a RAR (MSG 2) is received from the network, and the transmitted RACH preamble is explicitly signaled by the network. If so, monitor the downlink channel (PDCCH) until the C-RNTI received from the network indicates a new transmission, or the transmitted RACH preamble is not explicitly signaled by the network. If determined, a method for performing discontinuous reception (DRX) including starting a contention resolution timer is provided.

  The features described in this specification are summarized below.

  A method for performing a random access procedure in a mobile communication system including a network and a mobile terminal, the method being performed by the mobile terminal, transmitting a random access channel (RACH) preamble to the network, and the RACH preamble. Receiving from the network a RACH response notifying that the RACH preamble has been received, and using information included in the RACH response depending on whether the RACH preamble is contention-based or non-contention-based. Monitoring a channel; checking whether the random access preamble is contention based or non-contention based; and whether the random access preamble is contention based or non-contention. And performing a discontinuous reception procedure according to whether it is based.

  Here, the information included in the RACH response is used to determine whether the random access preamble is contention based or non-contention based. The monitoring is performed until the C-RNTI received from the network indicates a new transmission.

  A method of performing discontinuous reception (DRX) in mobile communication using a network and a mobile terminal, the method transmitting a RACH preamble to the network and receiving a random access response (MSG 2) from the network And, if it is determined that the transmitted RACH preamble has been explicitly signaled by the network, monitor the downlink channel (PDCCH) until the C-RNTI received from the network indicates a new transmission Or starting a contention resolution timer if it is determined that the transmitted RACH preamble is not explicitly signaled by the network.

  The RACH preamble explicitly signaled by the network is a preamble not selected by the UE MAC. The RACH preamble explicitly signaled by the network is information included in the PDCCH state.

  A method for performing a discontinuous reception (DRX) procedure in a mobile communication system including a network and a mobile terminal, wherein the method is performed by the mobile terminal and performs a random access procedure by transmitting a random access preamble to the network. Starting, receiving a random access response from the network notifying that the random access preamble has been received, and confirming whether the random access preamble is contention based or non-contention based And performing a discontinuous reception procedure according to whether the random access preamble is contention-based or non-contention-based.

  The discontinuous reception procedure is performed by monitoring a downlink channel (PDCCH) when the random access preamble is non-contention based and starting a contention resolution timer when the random access preamble is contention based. The mobile terminal performs a random access procedure when at least one of the following conditions is satisfied. When initial connection is made when there is no radio resource control (RRC) with the base station. When the mobile terminal initially connects to the target cell during handover. When requested by the base station. When uplink data occurs. If uplink time synchronization is not accurate or has not yet been assigned the specified radio resource used for the appropriate radio resource request. During the radio link failure or handover failure correction, decoding or reconfiguration procedure.

  In addition, the features described in this specification can be summarized as follows.

  A method of performing a random access procedure between a mobile terminal and a network, the method using a step of transmitting a random access channel (RACH) preamble to the network and information included in a RACH response received from the network Monitoring a downlink channel.

  The monitoring step includes a step of determining whether the MAC entity of the mobile terminal has selected a RACH preamble using information included in the RACH response. If it is determined that the RACH preamble has been explicitly signaled by the network, the downlink channel is further monitored until the C-RNTI received from the network indicates a new transmission. The method further includes starting a contention resolution timer if it is determined that the RACH preamble has been selected by a MAC entity of a mobile terminal. The downlink channel is a PDCCH.

  A method for performing a random access procedure between a mobile terminal and a network, the method comprising: transmitting a random access channel (RACH) preamble to the network; receiving a RACH response from the network; and the RACH preamble includes: If explicitly signaled by the network, monitoring the downlink channel until new transmission is indicated according to the radio resource allocation information received from the network, and the RACH preamble is selected by the MAC entity of the mobile terminal A contention resolution timer is started.

  If the contention resolution timer expires, no further downlink channels are monitored. The downlink channel is a PDCCH. The method further includes using information included in the RACH response to determine whether the RACH preamble has been explicitly signaled by the network or selected by the MAC entity of the mobile terminal. The radio resource allocation information is C-RNTI.

  A method for performing a random access procedure between a mobile terminal and a network, the method comprising: transmitting a random access channel (RACH) preamble to the network; receiving a RACH response from the network; and the RACH preamble includes: Determining whether explicitly signaled by the network and, if the RACH preamble is explicitly signaled by the network, downlink until a new transmission is indicated according to radio resource allocation information received from the network Monitoring a channel and starting a contention resolution timer if the RACH preamble is not explicitly signaled by the network.

  The radio resource allocation information is C-RNTI. The downlink channel is a PDCCH. If the contention resolution timer expires, no further downlink channels are monitored.

  The mobile terminal sends a RACH preamble to the network, receives a RACH response from the network, determines whether the RACH preamble is explicitly signaled by the network, and the RACH preamble is explicitly signaled by the network A communication module that monitors the downlink channel until new transmission is indicated according to radio resource allocation information received from the network and starts a contention resolution timer if the RACH preamble is selected by the MAC entity of the mobile terminal including.

  Various features and concepts described herein may be implemented as software, hardware, or a combination thereof. For example, a computer program (executed by a computer, terminal or network device) for a method and system for performing a random access procedure between a mobile terminal and a network based on the characteristics of a RACH preamble is one that performs various functions. Alternatively, it may be composed of a plurality of program code portions. Similarly, a software tool (executed by a computer, terminal or network device) for a method and system for performing a random access procedure between a mobile terminal and a network based on the characteristics of a RACH preamble is a program that performs various functions. It may consist of a code part.

  The method and system for processing Buffer Status Reports (BSRs) according to the present invention is compatible with various types of technologies and standards. Some features described herein relate to various types of standards such as GSM, 3GPP, LTE, IEEE, 4G. It will be appreciated that the standards illustrated above are not limiting and that other related standards and techniques may be applied to the various features and concepts described herein.

  The various features and concepts described herein are different types of user equipment (eg, mobile terminals, mobile phones, mobile phones, mobile phones, etc.) configured to perform random access procedures in a mobile communication system. It can be applied and realized in a wireless communication device etc.) and / or a network entity.

The present invention also provides the following items, for example.
(Item 1)
Transmitting a RACH (Random Access CHannel) preamble to the network;
Monitoring a downlink channel using information included in a RACH response received from the network;
A random access procedure between the mobile terminal and the network.
(Item 2)
The mobile terminal of claim 1, wherein the monitoring step further comprises determining whether the RACH preamble is selected by a MAC entity of the mobile terminal using information included in the RACH response. A random access procedure between the network and the network.
(Item 3)
If the RACH preamble is determined to be explicitly signaled by the network, the downlink channel is further monitored until a new transmission is indicated by a C-RNTI received from the network. A method of performing a random access procedure between the described mobile terminal and the network.
(Item 4)
The mobile terminal according to claim 2, further comprising a step of starting a contention resolution timer when it is determined that the RACH preamble is selected by a MAC entity of the mobile terminal. How to do a random access procedure.
(Item 5)
2. The method for performing a random access procedure between a mobile terminal and a network according to item 1, wherein the downlink channel is a PDCCH (Physical Downlink Control CHannel).
(Item 6)
Transmitting a RACH (Random Access CHannel) preamble to the network;
Receiving a RACH response from the network;
If the RACH preamble is determined to be explicitly signaled by the network, monitoring a downlink channel until a new transmission is indicated according to radio resource allocation information received from the network;
Starting a contention resolution timer if the RACH preamble is selected by a MAC entity of the mobile terminal;
A random access procedure between the mobile terminal and the network.
(Item 7)
The method according to claim 6, wherein when the contention resolution timer expires, the downlink channel is no longer monitored.
(Item 8)
7. The method for performing a random access procedure between a mobile terminal and a network according to item 6, wherein the downlink channel is a PDCCH (Physical Downlink Control CHannel).
(Item 9)
Item 6 further comprising determining whether the RACH preamble is explicitly signaled by the network or selected by the MAC entity of the mobile terminal using information included in the RACH response. A method for performing a random access procedure between the mobile terminal and the network described in 1.
(Item 10)
7. The method for performing a random access procedure between a mobile terminal and a network according to item 6, wherein the radio resource allocation information is C-RNTI (Radio Network Temporary Identifier).
(Item 11)
Transmitting a RACH (Random Access CHannel) preamble to the network;
Receiving a RACH response from the network;
Determining whether the RACH preamble has been explicitly signaled by the network;
Monitoring the downlink channel until a new transmission is indicated according to radio resource allocation information received from the network if the RACH preamble is explicitly signaled by the network;
Starting a contention resolution timer if the RACH preamble is not explicitly signaled by the network;
A random access procedure between the mobile terminal and the network.
(Item 12)
12. The method for performing a random access procedure between a mobile terminal and a network according to item 11, wherein the radio resource allocation information is C-RNTI (Radio Network Temporary Identifier).
(Item 13)
12. The method for performing a random access procedure between a mobile terminal and a network according to item 11, wherein the downlink channel is a PDCCH (Physical Downlink Control CHannel).
(Item 14)
The method of claim 11, wherein when the contention resolution timer expires, the downlink channel is no longer monitored.
(Item 15)
It sends a RACH (Random Access CHannel) preamble to the network, receives a RACH response from the network, determines whether the RACH preamble is explicitly signaled by the network, and the RACH preamble is explicitly signaled by the network. In the case of the communication, the downlink channel is monitored until new transmission is indicated according to the radio resource allocation information received from the network, and the contention resolution timer is started when the RACH preamble is selected by the MAC entity of the mobile terminal A mobile terminal comprising a module.
Since various concepts and features described in this specification can be realized in various forms without departing from the features, the above embodiments should not be limited by the details of the above description unless otherwise specified. Should be construed broadly within the scope defined in the following claims. Accordingly, all changes and modifications belonging to the scope or equivalent thereof are considered to be included in the appended claims.

Claims (11)

A method of performing a random access procedure between a mobile terminal and a network,
The method
And transmitting a random access preamble to the network,
Receiving a random access response from the network,
Wherein when the random access preamble is by interest signaling to the network, the new transmission in response to network or al-free line resource allocation information to indicate to the downlink channel is received, DRX (Discontinuous Reception) active time and monitoring a downlink channel according to,
If the random access preamble is selected by the MAC (Medium Access Control) entity of the mobile terminal starts a contention resolution timer, and that the contention resolution timer to monitor the downlink channel until the expiration or stopped Including a method. When the monitoring was successful, it stops the contention resolution timer, the method according to claim 1. The downlink channel is a PDCCH (Physical Downlink Control CHannel), The method of claim 1. Using the information included in the random access response, the one random access preamble is by interest signaling to the network, further comprises determining whether selected by the MAC entity of the mobile terminal, in claim 1 The method described. The radio resource allocation information is C-RNTI (Common- Radio Network Temporary Identifier), The method of claim 1. A method of performing a random access procedure between a mobile terminal and a network,
The method
And transmitting a random access preamble to the network,
Receiving a random access response from the network,
And that the random access preamble is determined whether or not a by interest signaling to the network,
Wherein when the random access preamble is by interest signaling to the network, the new transmission in response to network or al-free line resource allocation information to indicate to the downlink channel is received, DRX (Discontinuous Reception) active time and monitoring a downlink channel according to,
Wherein when the random access preamble is not by interest signaling to the network, to start a Contention Resolution Timer, and a monitoring a downlink channel until the contention resolution timer expires or stops, method. The radio resource allocation information is C-RNTI (Common- Radio Network Temporary Identifier), The method of claim 6. The downlink channel is a PDCCH (Physical Downlink Control CHannel), The method of claim 6. The method of claim 6 , wherein the contention resolution timer is stopped if the monitor is successful . A mobile terminal performing a random access procedure,
The mobile terminal
A microprocessor configured to control the random access procedure;
A communication module configured to operate based on control from the microprocessor;
With
The microprocessor is
Transmitting a random access preamble to the network via the communication module ;
Receiving a random access response from the network via the communication network ;
Wherein when the random access preamble is by interest signaling to the network, the new transmission in response to network or al-free line resource allocation information to indicate to the downlink channel is received, DRX (Discontinuous Reception) active time Monitoring the downlink channel according to
If the random access preamble is selected by the MAC (Medium Access Control) entity of the mobile terminal starts a contention resolution timer, and that the contention resolution timer to monitor the downlink channel until the expiration or stopped
A mobile terminal configured to perform . The mobile terminal according to claim 10, wherein the contention resolution timer is stopped when the monitoring is successful.

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